The present invention relates to a two-lobed filter bag for products for infusion, such as tea, chamomile and similar products.
The constant increase over time in the use of filter bags for products for infusion, both in private households and in public establishments, has lead to increasing research, especially by product distributors, into the differentiation of the individual package, improving its product holding capacity, its exchange with the liquid during the infusion time, its shelf life, ease of final packaging, etc.
For example, the original single lobe bag with pick-up label was succeeded by the classic and now established two-lobed bag (again with thread and label, with or without individual wrapper), whose special feature is improved release of the product, thanks to the greater surface for contact with the liquid; this type of bag being of particular interest in the present text.
To these product requirements relative to its commercial aspect are added the requirements of the production sector, that tend, as far as possible, to simplify the machines for the manufacture of such two-lobed bags, whose final construction is not simple. In an attempt to reduce the cost of the individual products, manufacturers employed solutions which could increase the productivity of the machines, or other solutions which could use diverse basic products. For example, the use of heat-sealable or non-heat-sealable filter paper, elements which seal the bags using a metal staple, gluing or xe2x80x9cadditional blobsxe2x80x9d of heat-sealable material and the use of adhesive or non-adhesive labels.
The present text does not refer to the sector of the classic two-lobed bag sealed and attached to the thread and label using metal staples. Amongst the solutions which envisage the use of heat-sealable filter paper, the technique illustrated, for example, in patent IT-1.187.308 is known, in which the two-lobed bags are obtained from a continuous sheet of filter paper, upon which a succession of doses are placed, at equal distances from one another then, for each bag, a tubular section of filter paper is defined during a tube forming stage in which it is closed by folding and longitudinal sealing.
The two pockets of the bag are defined by a series of transversal seals, creating separate pockets or lobes, each with a base and free end. A continuously fed thread is then positioned centrally and longitudinally on the tubular sheet, labels already being attached to the thread, at regular intervals, by a blob of heat-sealable material.
Positioning of the thread is followed by a stage in which the tubular sheet is cut to define a tubular section comprising two pockets or lobes and a length of thread, the ends of which are attached to the free ends of the pockets by the above-mentioned blob of heat-sealable material. In the center of the section thus obtained a characteristic xe2x80x9cWxe2x80x9d-shaped fold is then made, allowing separation of the two opposite lobes or chambers. The two lobes are then rotated about the fold, until they are alongside one another, then they are stably joined by heat-sealing to form the filter bag as a whole, that is to say, with a thread extending longitudinally and wrapped around the package.
In a different solution, see patent EP-448.325, the filter bag comprises two chambers or lobes obtained from a pair of sheets, fed one above the other, following the depositing of product doses, and heat-sealed at the edges, then folded one towards the other with the characteristic xe2x80x9cWxe2x80x9d-shaped fold. As in the previous case, the thread to which the label is attached may be wound longitudinally around the filter bag with its ends heat-sealed to the relative surfaces, or may be positioned on a single surface of the filter bag and gathered there under the pick-up label, which also serves to hold the thread in place.
Over time, such types of filter bags have displayed disadvantages due, in particular, to the complexity of the solution which uses the blob of heat-sealable material, the fragility of the zone at which the surface of the filter bag and the end of the thread are joined (normally by heat-sealing or blobs of gluexe2x80x94in a concentrated zone) and the shortness of the threadxe2x80x94joined to the length of the bag, as indicated abovexe2x80x94for some infusion operations necessary, where very tall containers are used. The fragility of the join may cause the thread to be detached from the filter bag during preparation of the infusion or as it is removed from the container, whilst the shortness of the thread limits the conventional infusion maneuver, increasing the risk of the user being scalded.
The aim of the present invention is, therefore, to overcome the above-mentioned disadvantages by providing a filter bag which is practical and convenient to use, without changing those features of the typical two-lobed filter bag that are already good.